How to save data from many PC to one table SQL

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C#

ASP.NET

SQL-Server

I want to save some data to one table from many PC. But the data have a index(ID) that fill manually and order from previous data(ID), so I check it first on database then increment it.The problem is If more than one PC/device save together, it will save with same result. How to solve this problem?

What I have tried:

This is query for search the last ID that used:

public DataRow GetPlayerIDByClient(object clientPK)
       {
           DataRow result = null;

           if (clientPK != null)
           {
               IDbDataParameter clientFKParam = this.CreateParameter(csPlayerNamesEntity.Names.ClientFK, clientPK);

               string selectCommand = string.Format("SELECT TOP 1 * FROM {0} WHERE {1} = {3} AND " +
                                                       "({2} LIKE 'G%' or {2} LIKE 'g%') ORDER BY {4} DESC",
                                                       csPlayerNamesEntity.Names.TableName, //0
                                                       csPlayerNamesEntity.Names.ClientFK, //1
                                                       csPlayerNamesEntity.Names.ID,//2
                                                       clientFKParam,//3
                                                       csPlayerNamesEntity.Names.PK); //4

               DataTable dt = this.ExecReaderDataTable(selectCommand, clientFKParam);

               if (dt != null && dt.Rows.Count > 0)
               {
                   result = dt.Rows[0];
               }
           }

           return result;
       }